GPA needs to be about a 3.8 at least, overall. And if that is weighted by AP classes they will adjust it down to equalize and then consider that you went above and beyond. That's why you need as many A's and as many AP classes as possible.
Math and science are critical but the ACAD's value english and history too because every day you will asked about military history, facts, trivia, etc.
Sports are critical--you have to play at least one varsity sport and earn a letter and probably need two sports. You have to pass a rigorous CFA fitness test--50 pushups, 70 situps, 10 pullups, throw a basketball 70 feet from your knees, run a shuttle run between two 10 yard markers in less than 10 secs (4times back and forth I think,) and run the mile in something in the 6:00 minute to 7:00 minute range.
You need letters of recommendation from teachers and if you can get them, from military personnel who know you well.
You need to write solid essays. You should be able to communicate very clearly why you want to serve, why you want to be an officer, and why you want to attend the ACAD's.
Most importantly you need to be of fine character--and I do mean fine. No blemishes of any kind. You need to be active in the community and volunteer as well as in school in actvities such as student government. You need to be a leader and have others vouch that you are. Work at some part time job.
Also, if 1720 is your combined reading math and writing score it's too low. You need to be over 1900. You are on the line with 1720--and I mean the minimum's they state on the Congressinal nomination sites and on the ACAD's web sites. Forget averages and minimums, this is a highly competitive dogfight. You also need to be in the top 10% of your class.
You may think you have time but they don't consider the senior year grades--at least the AFA doesn't and I think the NA only takes a double-check look at 7th semester, although they can hurt you if you slack off after an appointment--they can withdraw it. So with one and a half years left it would be mathmatically difficult to get a 2.6 to a 3.7 or so.
Also get to know your counselor very well and your PE teachers as they will have to administer the CFA. Start cultivating recommendations. Tutor. Teach something to someone.
Practice public speaking and start thinking about interview questions and answers because you are going to have to interview with Liason officers from each Academy as well as your Congressmen's decision panel for the nomination. Always dress in a sharp suit even if they say casual is ok. Attend Academy Night openhouses in your area and bring your parents. Make an impression. Always be selling them on you. Keep in touch with all of your contacts. They want to know you really want this.
You need to go to the websites and read the class profiles and also fill out the request for info / pre candidate elligibility forms. You have to get started on this now. They won't even give you an application unless you are considered eligible. Although you might want to wait until you meet their minimum requirements before you complete and submit it--check to make sure you do--minimums are just that--price of entry just to apply--they are not to be confused with what is really going to get you in.
You also have to pass a DOD physical and have good hearing and good vision. If you've had optical surgery already you won't get in. Defer anything like that.
It's very difficult to get in but it can be done. It's something you really have to aim for before you even get to HS. There are exceptions of course. You just can't expect to be average and do it--unless you are a top all american sports star in H.S. Then you can have a 2.6 and probably even lower than that.
I don't mean to discourage you because you should go for it if it is your dream. But you have an uphill battle and don't let anyone tell you you don't or that it takes less than what I am describing to be relatively assured of being competetive for an appointment. You will be sorely disappointment if you listen to them. So it's gonna be tough. So what? You don't belong in there if you can't take "tough." Just a question of how bad do you want it.
You should also consider ROTC. You can still become a pilot if that's what you want and if you earn an ROTC scholarship award you will have college paid for (mostly.) It might be a LITTLE easier to win an ROTC award.
Seriously. You need to pick a sport and get on the H.S. team ASAP.
Take an SAT class. Invest in class that guarantees a 200 point increase--I think it's the Princeton Review Class--costs about a grand though. Run for office at school. Join Junior Statesmen of America and debate at the conventions. Volunteer, Tutor. Run five miles a night. Work on the weekends, and if you can find the time and the money, take five hours of flying lessons.
How bad do you want it?
Good luck!